Electrons in an atom can be classified as core electrons and valence electrons. Valence electrons are those electrons which are present in valence shell and participates in bond formation. While, Core electrons are all remaining electrons which are not present in valence shell, hence not take part in bonding.
Atomic number of Selenium (Se) is 34 hence it has 34 electrons with following electronic configuration;
1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁴
From electronic configuration it is found that the valence shell is 4, and the number of electrons present in valence shell are 6. So,
Core Electrons = Total Electrons - Valence Electrons
Core Electrons = 34 - 6
Core Electrons = 28
Result:
There are 28 core electrons in Selenium.
Answer:
3
Explanation:
If we want it to be rounded to one significant figure, it will be 3.
Answer:
The answer to your question is letter D.
Explanation:
Bohr tells us that the electrons which have a negative charge clicle the orbits in specific nucleus, so the right answer is letter D.
Letter C is not possible because the electrons are in orbits circling the nucleus where the protons are.
Letter B is not correct because electrons are distributed in orbits but the amount of electrons in one orbit is different to the other one.
Answer:
Explanation:
Hello,
In this case, the undergoing chemical reaction is:
Next, we compute the reacting moles of each reactants:
Then, as magnesium and hydrohloric acid are in a 1:2 molar ratio 0.153 moles of magnesium will completely react with 0.306 moles of hydrochloric acid yet we only have 0.144 moles, therefore, limiting reactant is hydrochloric acid. Thus, we compute the produced moles of hydrogen:
Finally, we use the ideal gas equation with T=298K and 1atm (STP conditions) to compute the liters of hydrogen gas:
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